<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <div id="root"></div>
  <script src="./lib/react.js"></script>
  <script src="./lib/react_dom.js"></script>
  <script src="./lib/babel.js"></script>
  <script type="text/babel">
    const root = ReactDOM.createRoot(document.querySelector("#root"))
    let message = "Hello World"
    function btnClick(){
      message = "Hello React"
      // 重新渲染
      rootclick()
    }
    function rootclick(){
      root.render((
      <div>
        <h2>{message}</h2>  
        <button onClick={btnClick}>修改文本</button>
      </div>
    ))
    }
    rootclick()
  </script>
</body>

</html>